Tips for Growing Tomatoes in the Pacific Northwest

One thing I get asked about a lot, is how to grow good tomatoes here in Seattle. With the cooler climate and short “warm season” in the Pacific Northwest, growing tomatoes can be tricky. In an effort to learn what works best, I have planted my tomatoes with slight variations every year. There has definitely been a lot of trial and error. Below is a list of what has proven to work well for me over the years and a few tips on what NOT to do as well.

1. A couple of weeks before I plan on planting my tomatoes, I heat the soil by covering it with plastic. That will start tomatoes off right and give them the soil warmth they love. If it’s a particularly cold year, I might keep my plants inside until it warms up more. That involves up potting the plants and staking them (as pictured below), so it’s an added step and not my preferred method.

2. I try to pick good varieties that do well in my area. I usually only have room for about six plants, so I don’t want to buy a whole pack of seeds for just six plants. I also want several different varieties, so I always just buy starts. I like to get my starts at the Seattle Tilth Edible Plant Sale. They only carry varieties that will do well in this region and there are so many to choose from. Unfortunately, the sale already happened for this year*, but the vegetable list which has all the tomato varieties they carried listed (with great descriptions), can be still downloaded from their website, so it would still be a good place to start researching varieties.

*Tips for next year’s sale though, are to prepick what varieties you want ahead of time. I usually just pick based on the descriptions and whatever has won a tomato tasting contest (held at the Harvest Fair every year). Some of the more popular varieties (such as Sungold cherry tomatoes) sell out, so if you are dead set on a particular variety, get there early.

3. Plant in full sun. An ideal scenario for tomatoes would be an area that gets full sun and is near a wall that will warm up (and transfer heat to the tomatoes) and block wind.

4. Plant with proper amendments. I always amend all my beds with organic fertilizer in the Spring, but my tomatoes get more amendments when I plant them. For my planting hole, I dig it wide and deep. I then set the transplant, so it’s bottom set of leaves are at soil level. To each planting hole, I add a few inches of sifted compost, a handful of bone meal and a teaspoon of Epsom salts (for magnesium, which promotes productivity). I install my cages at the time of planting as well, so as not to disturb the roots.

5. I avoid transplant shock and keep the plants warm by covering them with plastic. I found some 33 gallon clear plastic bags that are just the right size and work great. I poke a few holes at the top to allow water to get through, so it doesn’t weigh the bag down and cause it to sink into the cage. I also use small binder clips at the bottom of the cage to keep it from blowing off.

6. When planting tomatoes make sure you give them enough space, usually 2-3 feet at least.If you do all this other stuff (keep them warm, fertilize, etc.), your plants will get big, which is great, that’s what we want, but big plants with not enough space between them, don’t get enough airflow and will promote the spread of disease.

7. I have heard of more aggressive pruning tactics, but I usually just remove the suckers (the new shoots that emerge from main and side stems). I just twist them off with my fingers when they are small. If they get too big to do that, I leave them, so as not to open up an opportunity for disease. I also leave some at the top, once the plant is big, to provide a little shade for the rest of the plant. I do however, start to remove blossoms late in the growing season (when it seems like they won’t have enough time to mature), so that they don’t take energy away from fruit that still needs to ripen.

8.I learned my lesson about the importance of even watering last year, when I got blossom end rot, which is caused by uneven watering. These pictures are all from last year when I planted them in containers. Tomatoes can do fine in containers (as long as they are large enough), just don’t forget to water them like I did. This year, they are back in the raised bed, which is on a drip irrigation system on a timer, so I won’t forget. Watering in general is a whole ‘nother subject I have yet to cover, so I will save that for another post.

9.Lastly, I fertilize during growing season withliquid seaweed. I just add a couple of capfuls to the watering can and add it that way, usually every couple of weeks. Side dressing with compost can also be good and act as a nice mulch that retains moisture.

Then if all goes well, I have enough tomatoes for sauce, snacking, sharing and my favorite zucchini tomato tart!

Do you have other tried and true methods for great tomatoes? Or varieties you really love? I would love to hear them!

You can totally follow the post planting tips! All you would have missed is adding the bone meal and the epsom salts. Depending on how big your plants are now, you could probably still put a wall o’ water over them or plastic if you installed a tomato cage. I can’t remember if I bought my liquid seaweed extract at McLendon’s or the West Seattle Nursery, but it was one of those two!

Thanks for this really helpful post! We’re in New England so we have some of the same issues (hotter summers here but same short growing season) – hadn’t heard about the epsom salt before and wouldn’t have thought of something as simple as removing flowers towards the end of the season!

Hi Miya! I lived in New England when I was a kid and I love it out East! I do remember real seasons out there. Cold snowy winters and hot mosquito filled summers. My boyfriend’s mom lives in Vermont and has a garden, so we do share stories about that. I am usually planting earlier than her, since I don’t have to wait for snow to melt like she does Oh and I checked out your blog. My boyfriend has done a little home brewing (and recently built a “keezer”), so I am totally going to show your blog to him! And I’ll be back to it for the other subjects, so thanks for commenting!

Yes! Good list! I love it. I’m down here South of Seattle and have found that when I move my little transplants outside to cover them with plastic is critical – I like your covers! This year I re-purposed old soil bags turned inside out – has worked like a charm – the tomato plants are monstrous in there! I also grow my indeterminates in large pots against the sunniest wall possible and then train them up the wall with twine and stuff. I heard a tip that around here that we should prune well, give plenty of room, water deep at intervals, but STOP watering at the start of august, so that all the energy of the plant goes into fruit production and sweetening the fruit. I don’t know. I’m gonna try it this year with some and see what happens! August nowadays is getting pretty hot and dry so that might be a disaster….

I just found your blog and am so glad I did. I’m always looking to read more northwest bloggers – we are all dealing with the same thing at the same time!

Hi Lindsey! Great tips! I love that you repurposed soil bags, what a great idea. I also want to try your watering tip or maybe just water less towards the end? I know that is what they say to do with snap peas.
I checked out your blog as well. It’s so cool to see what other people are doing in their gardens. Your on my Bloglovin’ now, so I’m a regular reader now!

Thanks for the info. After recently moving back to the Gig Harbor area from Portland, OR I have been struggling with my garden and tomatoes. This year seems to be a better year. I have also found Walls Of Water to be wonderful insulator for my plants and can usually plant them a couple of weeks earlier with these. They are a wall of tubular cells that you fill with water, the sun heats the water and then insulates the plant during those unexpected cool or frosty nights. I have used them for years and wouldn’t plant my tomatoes without them, especially now in Washington.

Ah tomatoes, I still have a pile ripening(or not) as I had to pick them all when the weather turned foul. I planted them too late this year and they did not get really hot and start producing until late August into September, then it turned cold, got blossom rot etc. My neighbour grows tomatoes mostly in a greenhouse(home made and cute), so when she went away and I was cat sitting, she gave me piles of ripe ones to eat. yum.
I find in the PNW, that it gets really nice in early May and everyone goes about like mad planting and dreaming of the things that will grow. Then June comes along and it rains and is cold/grey the entire month. I have found that if I plant in May, the June rains ruin everything, so often replant or just wait until July. Given the warm season can be very brief this often a recipe for heartache. So, I will plant seeds indoors, or keep bedding plants indoors until I think it is safe to go out. Due to blight problems I planted my tomatoes in a new garden bed that seemed to get a good deal of sun despite the wall of cedars all around.
I think having a greenhouse is the best way to go. Alternatively, I always have some tomato plants in pots that live on the sunniest part of the deck next to the house and under the roof overhang which offers protection from the rain.

Hi John. Glad you found my blog (and like it) and thanks for commenting. Good question about how long I keep the plastic on. It varies depending on the weather that year, but I think I usually take it off in late June/early July. I judge it by when the weather has warmed up (and stays warmish at night) and the plant gets so tall and wide that it needs the extra room to grow. Hopefully those things happen around the same time!

I keep the plastic on 24 hours, until it warms up, which usually ends up being about the same time the plants are taller than the cages. By then, they need the plastic to come off so they can have room to grow. That’s usually about July for us here in Pacific Northwest. I also take a pair of scissors and cut some holes in the top of the plastic bags for vents and so that rain can get through. Hope that answers your question!

I have been growing tomatoes in the Pacific Northwesr for 30 years with great success. Blosm end rot has been a problem if you experience this problem the cure is a handful of sweet lime worked into the soil when planting. Your advise is terrific.

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Rake and Make is a Seattle, WA. based blog, so I’m gardening in the Northwest climate. I live with my husband, a dog, a cat and four chickens, named Camilla, Lorraine, Florence and Rita. What started out as a gardening blog has grown to include all the things I like to make, whether it's gardening, cooking or craft related. Please comment, subscribe and/or follow me on social media!